The Assignee of the present application has a pending application, U.S. Patent Application Ser. No. 116,194 filed on Nov. 3, 1987 which is a continuation-in-part application of U.S. Pat. Application Ser. No. 041,169, filed Apr. 22, 1987 which describes apparatus and methods for removing finely particulate surface contaminants from a substrate such as a semiconductor wafer.
The apparatus, as shown in particular in the drawings, provides for the flow of fluid carbon dioxide into a chamber wherein the fluid is converted to a mixture of gaseous carbon dioxide and fine droplets of carbon dioxide. This mixture is then transported in metered amounts through the use of e.g. needle valve or a restricted orifice to a coalescing chamber where the fine droplets are converted to larger droplets to form a second mixture. The larger droplets are then formed into solid particles as the feed passes from the coalescing chamber through a tubular passageway into a second orifice and out of an exit port. The entire disclosure of U.S. Ser. No. 116,194 is incorporated herein by reference.
The apparatus of the present invention represents an improvement over the apparatus described above in that it is easier to manufacture, provides a more reliable means for metering the mixture and provides for more even distribution of the mixture, especially as it flows into the coalescing chamber. Another benefit of the present invention is that the solid product stream is directed out of the exit port and onto the substrate to provide more uniform cleaning. Cleaning is enhanced by employing an ejection port which has a slit-like shape and may be made of any desired width. The larger the width, the greater the cleaning area per pass.
In accordance with this invention there is provided a novel apparatus for removing small particles from a substrate which provides more effective means of controlling the flow rate of the fluid mixtures and thereby provide a more effective means of removing contaminants from a substrate surface.